In chemistry, the group (also known as family ) is the elemental column in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table, and the f-block columns (between groups 3 and 4) are not numbered. The elements in the group have similar physical or chemical characteristics of the outermost electron shell of their atom (ie, the same core charge), since most chemical properties are dominated by the orbital location of the outer electron. There are three group numbering systems. The modern numbering group 1 to group 18 is recommended by the International Union of Pure and Applied Chemistry (IUPAC). This replaces two older, confusing naming schemes. Also, groups can be identified by their top element or have a specific name. For example, group 16 is variously described as oxygen group and as chalcogen .
Video Group (periodic table)
Nama grup
In history, some group name sets have been used:
Several other names have been proposed and used without getting wide acceptance: volatile metal for group 12; icosagens for group 13; crystalloid , adamantogen , and merylides for group 14; and aerogens for group 18.
Maps Group (periodic table)
CAS and old IUPAC numbering (A/B)
Two existing system group numbers exist: CAS (Chemical Abstracts Service) and old IUPAC . Both use numbers (Arabic or Roman) and the letters A and B . Both systems agree on numbers. The numbers show about the highest oxidation number of the elements in the group, and thus show the same chemistry with other elements of the same number. The number increases linearly for the most part, once to the left of the table, and once to the right (see List of oxidation status of elements), with some deviations in the transition metal. However, both systems use different letters. For example, potassium (K) has one valence electron. Therefore, it lies in group 1. Calcium (Ca) is in group 2, because it contains two valence electrons.
In the old IUPAC system, the letters A and B are assigned to the left (A) and right (B) of the table, while in CAS systems the letters A and B are defined for main group elements (A) and transition elements (B). The old IUPAC system is often used in Europe, while CAS is most common in America. The new IUPAC scheme was developed to replace both systems because they use the same name for different purposes. This new system only counts groups from left to right on the standard periodic table. The IUPAC proposal was first circulated in 1985 for public comment, and was subsequently included as part of the 1990 edition of the Inorganic Chemistry Nomenclature .
References
Further reading
- Scerri, E. R. (2007). Periodic table, story and significance . Oxford University Press. ISBN: 978-0-19-530573-9.
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